Package-on-package semiconductor device

ABSTRACT

Some embodiments relate to a semiconductor device. The semiconductor device includes a substrate and a first die coupled to a top surface of the substrate. A second die is coupled to a bottom surface of the substrate. A thermal contact pad couples the second die to the bottom surface of the substrate. The thermal contact pad electrically isolates the first die from the second die. A molding compound resides over the substrate and surrounds the first and second dies and the thermal contact pad.

REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. application Ser. No. 14/827,862 filed on Aug. 17, 2015, which is a Divisional of U.S. application Ser. No. 13/803,609, filed on Mar. 14, 2013 (now U.S. Pat. No. 9,111,896 issued on Aug. 18, 2015), which claims priority to U.S. Provisional Application No. 61/692,893, filed on Aug. 24, 2012, the contents of which are hereby incorporated by reference in their entireties.

BACKGROUND

A Package-on-package (PoP) semiconductor device is used for high density electronic devices, and typically includes a bottom package component and a top package component combined together to form the PoP semiconductor device. The bottom package component includes a bottom die attached to a bottom packaging substrate and the top package component includes a top die attached to a top packaging substrate. The bottom and top package components are coupled together by a set of conductive elements, e.g., solder balls. During operation of the PoP semiconductor device, the bottom die typically generates heat that can cause cracks within the conductive elements and damage to the top die which results in thermal stress and warpage of the PoP semiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1A is a cross sectional view of a top package and a bottom package of a package-on-package (PoP) semiconductor device in accordance with one or more embodiments;

FIG. 1B is a top view of a thermal contact pad of the PoP semiconductor device in FIG. 1 in accordance with one or more embodiments;

FIG. 2 is a cross sectional view of a top package and a bottom package of a PoP semiconductor device in accordance with one or more embodiments;

FIG. 3 is a cross sectional view of a top package and a bottom package of a PoP semiconductor device in accordance with one or more embodiments;

FIG. 4 is a cross sectional view of a top package and a bottom package of a PoP semiconductor device in accordance with one or more embodiments;

FIG. 5 is a cross sectional view of a top package and a bottom package of a PoP semiconductor device in accordance with one or more embodiments;

FIG. 6 is a cross sectional view of a bottom package in accordance with one or more embodiments;

FIG. 7 is a cross sectional view of a bottom package in accordance with one or more embodiments;

FIG. 8 is a cross sectional view of a bottom package in accordance with one or more embodiments;

FIGS. 9A through 9I are cross sectional views of a method of forming the PoP semiconductor device in FIG. 1 in accordance with one or more embodiments;

FIGS. 10A through 10F are cross sectional views of a method of forming a bottom package in FIGS. 6 and 7 in accordance with one or more embodiments; and

FIGS. 11A through 11H are cross sectional views of a method of forming bottom package in FIG. 8 in accordance with one or more embodiments.

DETAILED DESCRIPTION

The making and using of the embodiments of the disclosure are discussed in detail below. It should be appreciated, however, that the embodiments provide many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are examples, and are not intended to limit the scope of the disclosure.

In FIG. 1A, a package-on-package (PoP) semiconductor device 100 includes a first package (e.g., a top package 110). The top package 110 includes a packaging substrate 111 and a plurality of stacked dies 112 electrically connected to the packaging substrate 111 by wire-bonding. The dies 112 are wire-bonded to the packaging substrate 111 using conductive contacts 113 (e.g., metal contacts) on a top surface of each die of the stacked dies 112 and contacts 114 on the packaging substrate 111 and bond wires 115 connecting the contacts 113 and 114 together.

According to one or more embodiments, each die of the stacked dies 112 comprises a memory chip, a logic chip, or a processor chip. Further, although the plurality of stacked dies 12 only includes two dies, the present disclosure is not limited to the particular number of dies. The dies are not limited to being wire-bonded to the packaging substrate 111. Other methods for connecting the stacked die 112 to the packaging substrate 111 will be discussed below with reference to FIGS. 4 and 5. According to one or more embodiments, solder bumps, solder balls, copper pillars, conductive bumps, solder caps, conductive pillars, conductive balls, under-bump metallurgies, and/or other connector elements are usable to connect the stacked die 112 to the packaging substrate 111. In some embodiments, an underfill is in a gap between the stacked die 112 and the packaging substrate 111 to thereby reinforce the strength of the PoP structure 100.

The packaging substrate 111 is a laminated circuit board comprising alternating layers of non-conductive polymers, such as bismaleinide-triazine (BT), and patterned or non-patterned conductive layers. The packaging substrate 111 includes top contacts 114, conductive vias 117, and bottom contacts 118 for electrical connection to other components. Solder balls 119 are used to electrically or thermally connect the top package 110 to a second package (e.g., a bottom package 120). The solder balls 119 electrically conduct signals and power to the stacked die 112. In one or more embodiments, the solder balls 119 are replaced with other conductive elements, such as conductive bumps and conductive balls (as depicted in FIG. 2, for example).

Further, as shown in FIG. 1A, a first molding compound 121 is formed on the top package 110 and provides mechanical stiffness, thereby enhancing the mechanical strength of the PoP structure 100. The molding compound 121 is molded on the packaging substrate 111 using a compressive molding or transfer molding process, for example, and surrounds the stacked die 112, the conductive contacts 113, 114, and the bond wires 115. In one or more embodiments, a curing operation is performed to solidify the molding compound 121. The molding compound 121 includes a polymer-based material, an underfill, or an epoxy, for example.

The bottom package 120 is attached to the top package 110 and includes a die 122 on a lower substrate 123. The die 122 is electrically connected with the lower substrate 123 by conductive elements (e.g., 124 and 125). According to one or more embodiments, the lower substrate 123 is a single crystal silicon lower substrate having one or more conductive layers. In some embodiments, the substrate is a ceramic substrate or polymer substrate. In some embodiments, a lower substrate 123 is used during a wafer-level packaging (WLP) process to package many dies 122. In some embodiments, the entire packaging process, including attaching the bottom package 120 and the top package 110, is completed before the lower substrate 123 is diced. According to one or more embodiments, the substrate is used in various parts of the process as an interface between electrical connections. In some embodiments, the lower substrate is provided or formed over electrical contacts and includes dielectric material and conductive elements formed within the lower substrate and over the lower substrate.

According to one or more embodiments, the die 122 is a logic chip, a processor chip, a memory chip, or the like. In at least some embodiments, the conductive elements 124 are metal contacts and the conductive elements 125 are metal pillars formed of copper (Cu). Alternatively, according to other embodiments, the conductive elements 124 and 125 are solder bumps, solder balls, copper pillars, conductive bumps, solder caps, conductive balls, and under-bump metallurgies.

An electrical connection between the die 122 and other circuitry is provided by the conductive elements (e.g., solder balls 119) on one side of the lower substrate 123 and the conductive elements (e.g., solder balls 126) on the opposite side of the lower substrate 123.

During operation of the PoP structure 100, the top package 110 and the bottom package 120 generate heat. In some embodiments, the heat generated by the bottom package 120 is greater than that generated by the top package 110, and potentially causes damage to the top package 110. A seal ring 130 and a thermal contact pad 140 are provided between a top surface of the die 122 and a bottom surface of the packaging substrate 111 to minimize heat transfer from the bottom package 120 to the top package 110 and prevent thermal stress and warpage in the PoP structure 100. The seal ring 130 provides a seal to insulate the top package 110 from heat generated by the bottom package 120. The thermal contact pad 140 comprises at least one of an oxide material, a nitride material, a molding compound or a polymer material. According to one or more embodiments, the thermal contact pad 140 comprises an adhesive material, such as epoxy or tape. In other embodiments, the thermal contact pad 140 is another plastic or silicone material. According to various embodiments, suitable material for the thermal contact pad 140 has a thermal conductivity of about or less than 0.5 Watts/Celsius (W/° C.) and is suitable for semiconductor processing and use in a semiconductor device under various operating conditions.

FIG. 1B is a top view of section A-A of FIG. 1A. According to one or more embodiments, the thermal contact pad 140 is a non-continuous layer. That is, the thermal contact pad 140 does not cover an entire top surface of the die 122. As shown in FIG. 1B, the seal ring 130 and the thermal contact pad 140 are of a non-continuous layer (e.g., a hollow rectangular shape). In other embodiments, the thermal contact pad 140 is of a circular shape such as a ring, an X shape, checkered shape, or any other suitable shape for the purpose set forth herein. According to one or more embodiments, the thermal contact pad 140 is a solid, continuous material along the top surface of the die 122 and fills the area within the seal ring 130. In one or more embodiments, a thickness of the thermal contact pad 140 is greater than approximately 10 microns (μm).

A second molding compound 142 is molded on the lower substrate 123 and surrounds the bottom package 120 including the die 122, between the seal ring 130 and the thermal contact pad 140 (e.g., at an outside of the thermal contact pad 140 and interposed between portions (i.e. segments) of the thermal contact pad as shown in FIG. 1A). The second molding compound 142 also surrounds the conductive elements (e.g., solder balls 119) and is between the conductive elements (e.g., metal contacts 125), for example. In addition, the second molding compound 142 surrounds the top package 110 including a bottom and side surfaces of the packaging substrate 111 and the first molding compound 121. In at least some embodiments, the second molding compound 142 is formed using compressive molding or transfer molding. In one or more embodiments, a curing operation is performed to solidify the second molding compound 142. In at least some embodiments, the molding compound 142 includes a polymer-based material, an underfill, or an epoxy.

According to one or more embodiments, the present disclosure is not limited to the use of solder balls 119 for electrically connecting the top package 110 with the bottom package 120. FIG. 2 is a cross sectional view of a top package 110 and a bottom package 220 of a PoP semiconductor device 200 in accordance with one or more embodiments.

The PoP semiconductor device 200 includes top package 110 as depicted in FIG. 1 and a bottom package 220 having the same components as that of the bottom package 120 with the exception of the use of conductive pillars 229 in place of the solder balls 119.

Further, according to one or more embodiments, the present disclosure is not limited to the use of conductive vias 125 for electrically connecting the die 122 to the lower substrate 123. FIG. 3 is cross sectional view of a top package 110 and a bottom package 320 of a PoP semiconductor device 300 in accordance with one or more embodiments. The PoP semiconductor device 300 includes a top package 110 as depicted in FIG. 1 and a bottom package 320 having the same components as that of the bottom package 120 with the exception of the use of solders 325 in place of the conductive vias 125 for electrically connecting the die 122 to the lower substrate 123.

The present disclosure is also not limited to the stacked die configuration in the top package 110 as shown in FIGS. 1-3. In other embodiments, the dies are formed in a side-by-side parallel configuration as shown in FIG. 4.

FIG. 4 is cross sectional view of a top package 410 and a bottom package 420 of a PoP semiconductor device in accordance with one or more embodiments. The top package 410 includes at least a first die 412 and a second die 413 adjacent to each other on a first upper substrate 415. The first die 412 and the second die 413 are electrically connected with the first upper substrate 415 by conductive elements (e.g., vias 416 and contacts 417). In the current embodiment, bonding wires and contact pads are not used to electrically connect the first die 412 and the second die 413 to the first upper substrate 415.

The top package 410 and the bottom package 420 are electrically connected together by conductive elements (e.g., solder balls 425). The bottom package 420 includes a die 426 electrically connected with a second lower substrate 427 by conductive elements (e.g., vias 428 and contacts 429). A seal ring 430 is between the first upper substrate 415 and the die 426 of the bottom package 420. A thermal contact pad 440 is between the top package 410 and the bottom package 420. As shown, the thermal contact pad 440 is between a top surface of the die 426 and the first upper substrate 415 and adjacent to the seal ring 430. The thermal contact pad 440 is a non-continuous layer. A first molding compound 446 is one the first upper substrate 415 and surrounds the top package 410 including the first die 412 and the second die 413 and the conductive elements (e.g., metal vias 416 and metal contacts 417). A second molding compound 448 is provided on the second upper substrate 427. The second molding compound 448 surrounds the first molding compound 446. Further, the second molding compound 448 is between portions of the thermal contact pad 440 and the seal ring 430, and surrounds the conductive elements (e.g., solder balls 425, metal vias 428 and metal contacts 429).

Although the dies 412 and 413 are shown in a side-by-side configuration in FIG. 4, the present disclosure is not limited to the particular configuration. In alternative embodiments, the dies 412 and 413 can be in a stacked configuration as discussed below with reference to FIG. 5.

FIG. 5 is cross sectional view of a top package 510 and a bottom package 520 of a PoP semiconductor device 500 in accordance with one or more embodiments. The top and bottom package 510 and 520 of the PoP semiconductor device 500 include the same components as the PoP semiconductor device 400 shown in FIG. 4, with the exception that first and second dies 512 and 513 are in a stacked configuration. As shown in FIG. 5, according to one or more embodiments, the second die 513 is larger than the first die 512 and is stacked on a surface of the first die 512. The first die 512 is between the second die 513 and a first upper substrate 515. The first upper substrate 515 is smaller than the first upper substrate 415 shown in FIG. 4. The first and second dies 512 and 513 are electrically connected with the first upper substrate 515 by conductive elements (e.g., metal contacts 517 and metal pillars 518). The metal pillars 518 extend in a horizontal direction to facilitate the connection between the second die 513 and the first upper substrate 515. The first die 513 is connected with the first upper substrate 515 by conductive elements (e.g. metal vias 519). The top package 510 is electrically connected with the bottom package 510 by conductive elements (e.g., solder balls 525). The bottom package 520 includes a die 526 electrically connected with a second lower substrate 527 by conductive elements (e.g., metal vias 528 and metal contacts 529). A seal ring 530 and a thermal contact pad 540 are formed between the first upper substrate 515 and the die 526 to thermally isolate the top package 510 from the bottom package 520. A first molding compound 546 is one the first upper substrate 515 and surrounds the top package 510 including the first die 512 and the second die 513 and the conductive elements (e.g., metal vias 517 and metal contacts 519). A second molding compound 548 is provided on the second lower substrate 527. The second molding compound 548 surrounds the first molding compound 546, is between portions of the thermal contact pad 540 and the seal ring 530 between the top package 510 and the bottom package 520, and the conductive elements (e.g., solder balls 525, metal vias 528 and metal contacts 529).

The present disclosure is not limited to a bottom package of a PoP semiconductor device having only a single die. According to one or more embodiments, the bottom package includes more than one die in a stacked wafer level package (WLP) structure having a thermal contact pad sandwiched between the dies to provide thermal isolation between the dies.

FIG. 6 is cross sectional view of a bottom package 620 in accordance with one or more embodiments. The bottom package 620 has at least a first die 621 and a second die 622. The first die 621 is between the second die 622 and a lower substrate 625. The dies 621 and 622 are electrically connected with the lower substrate 625 by conductive elements (e.g., metal pillars 626, metal pads 627 and metal vias 628). The second die 622 is connected with the lower substrate 625 by the metal pillars 622 and metal pads 627. The first die 621 is electrically connected with the lower substrate 625 by the metal vias 628. According to one or more embodiments, the second die 622 is larger than the first die 621. The second die 622 extends parallel to the lower substrate 625 and is of a same length as the lower substrate 625. The first die 621 is between the metal vias 627. A seal ring 630 and a thermal contact pad 640 are sandwiched between the first die 621 and the second die 622 and provide thermal isolation. According to one or more embodiments, the thermal contact pad 640 is of a same configuration as the thermal contact pad 140 (FIG. 1). A molding compound 650 is between the lower substrate 625 and the second die 622, and between portions of the thermal contact pad 640 and the seal ring 630. Additional conductive elements (e.g., solder balls 655) are provided on a side of the lower substrate 625, opposite the side of the first and second dies 621 and 622.

FIG. 7 is a cross sectional view of a bottom package 720 in accordance with one or more other embodiments. The bottom package 720 includes the same components as the bottom package 620 (FIG. 6) with the exception that the thermal contact pad 740 is a continuous layer.

FIG. 8 is a cross sectional view of a bottom package 820 in accordance with one or more other embodiments. The bottom package 820 includes the same components as the bottom package 720 in a different configuration. The bottom package 820 includes a first die 821 and a second die 822. The second die 822 is electrically connected with a lower substrate 825 by conductive elements (e.g., metal contacts 826 and metal pillars 827). The metal pillars 827 extend in the horizontal direction to facilitate the connection between the second die 822 and the lower substrate 825. The first die 821 is electrically connected with the lower substrate 825 by conductive elements (e.g., metal vias 828). A thermal contact pad 840 of a continuous layer is sandwiched between the first die 821 and the second die 822. A molding compound 850 is on the lower substrate 825, and surrounds the first die 821 and the second die 822, and is between portions of the thermal contact pad 840 and a seal ring, and the conductive elements (e.g., metal pillars 827 and metal vias 828).

FIGS. 9A through 9I are cross sectional views of a method for forming a PoP semiconductor device such as the semiconductor device of FIG. 1 in accordance with one or more embodiments. In FIG. 9A, a thin adhesive layer 922 is deposited on a carrier 920 via a deposition process, to prepare the carrier 920 for processing. In FIG. 9B, a top package (e.g., top package 110 as depicted in FIG. 1, for example) is deposited on the carrier 920. Next, in FIGS. 9C through 9D, a bottom package (e.g., bottom package 120 as depicted in FIG. 1) is formed. In FIG. 9C, a grinding process is performed on a backside of a substrate 930 to form a die layer 931 (e.g., die 122), and a metal pad (e.g., an aluminum pad 932) is deposited on the die layer 931. A passivation layer 933 (a thin oxide layer) is deposited on the aluminum pad 932. The passivation layer 933 is etched to create trenches or vias and metal layer 934 is deposited within the trenches or vias for forming metal vias (e.g., metal vias 125). An underfill layer 935 formed of a polyimide (Pi) material then deposited on a surface of the passivation layer 933 and over the metal layer 934.

In FIG. 9D, a thermal contact material 940 is formed on the grinded surface of the die layer 931; and in FIG. 9E a thermal contact pad (e.g., thermal contact pad 140 as depicted in FIG. 1) is formed by etching or by sawing, laser grooving or mechanical sawing process. A singulation process is then performed to form separate bottom packages (e.g., bottom package 120).

In FIG. 9F, the bottom package 120 is disposed on the top package 110. The thermal contact pad 140 is aligned with a package substrate (e.g., package substrate 111) of the top package 110. A molding compound 142 is molded on the lower substrate 123 and surrounds the bottom package 120 including the die 122 and the thermal contact pad 140. The molding compound 142 also surrounds the conductive elements (e.g., solder balls 119 as shown in FIG. 1A) and the top package 110 including a bottom and side surfaces of the packaging substrate 111 and a molding compound of the top package 110 (e.g., first molding compound 121). In at least some embodiments, the molding compound 142 is formed using compressive molding or transfer molding.

In FIG. 9G, a multi-layer redistribution layer 923 is formed including the conductive elements. The top package 110 is then electrically connected with the bottom package 120 by the conductive elements 117, 118 and 119. In FIG. 9H, additional conductive elements 126 are then formed by ball mounting according to one or more embodiments for electrical connection to other circuitry.

In FIG. 9I, the formation of the PoP semiconductor device is complete and the carrier 920 is removed by a de-bonding process.

FIGS. 10A through 10F are cross sectional views of a method for forming a bottom package in FIGS. 6 and 7 in accordance with one or more embodiments.

In FIG. 10A, a first die 621 and second die 622 are formed. The second die 622 is larger than the first die 621. A thermal contact pad 640, 740 is between the first die 621 and the second die 622. Further, conductive elements (e.g., metal pillars 627 and metal vias 628) are formed. In FIG. 10B, a molding compound 650 is then deposited and molded to surround the first die 621, a top surface of the second die 62 and the conductive elements 627 and 628.

In FIG. 10C, an etching or grinding operation is performed on a surface of the molding compound. The molding compound is etched to a top surface of the conductive elements 628. In FIG. 10D, a lower substrate (e.g., 625) is formed or provided on a surface the molding compound and conductive elements (e.g., metal contacts 626) and are formed in and at an opposite surface of the lower substrate 625 and then the first and second dies are electrically connected with the lower substrate 625 by the conductive elements 626, 627 and 628. In FIG. 10E, conductive elements (e.g. solder balls 655) are formed to connect the bottom package to other circuitry (e.g., a top package). Then, in FIG. 10F, a singulation process (see dashed lines) is then performed to separate the bottom packages.

FIGS. 11A through 11H are cross sectional views of a method for forming a bottom package such as the bottom package of FIG. 8 in accordance with one or more embodiments.

In FIG. 11A, a carrier (e.g., carrier 920 shown in FIG. 9A, for example) is prepared for processing. A thin adhesive layer 922 is deposited on the carrier 920 by a deposition process. Then, in FIG. 11B, a first die 821 and a second die 822 are deposited on the carrier 920. A thermal contact pad 840 is between the first die 821 and the second die 822. Further, conductive elements (e.g., metal pillars 817 and metal vias 828) are formed.

In FIG. 11C, a molding compound is molded via a molding operation, to surround the first die 821, the second die 822, and the conductive elements 817 and 828. In FIG. 11D, etching or grinding operation is performed where the molding compound is etched to a surface of the conductive elements 817 and 828.

In FIG. 11E, a lower substrate 825 is formed on a surface the molding compound 850. Further, conductive elements (e.g., metal contacts 826) are formed at an opposite surface of the lower substrate 825 and the first and second dies 821 and 822 are connected with the PoP substrate 825 by the metal contacts 826. Conductive elements (e.g., solder balls 855) are then formed at a surface of the metal contacts 826.

The carrier 920 is then removed in FIG. 11G, by a de-bonding process and a singulation process (see dashed line) is then performed in FIG. 11H.

One or more embodiments include a method of forming a package-on-package semiconductor device encompassing a first package with at least one first die on a packaging substrate removably coupled to a carrier, forming a thermal contact pad on the first die package and bonding a second die package to the first die package where the thermal contact pad is between the two packages. The method further encompasses electrically coupling the first die package to the second die package with a set of conductive elements and removing the carrier from the first package.

One or more embodiments include a method of forming a semiconductor device by forming a top die package encompassing a plurality of first dies on a top packaging substrate and forming a bottom die package with at least one second die. A first set of conductive elements is used to electrically connect the top die package with the bottom die package; and a thermal contact pad is provided between the a top surface of the bottom die package and a bottom surface of the top packaging substrate. A molding compound is provided to surround the thermal contact pad, the top packaging substrate and the bottom die package.

One or more embodiments include a method of forming a semiconductor device, by forming a top die package encompassing at least two stacked dies on a top packing substrate, electrically coupling the at least two stacked dies to the top packaging substrate with a first set of conductive elements. Depositing a first molding compound on the top packaging substrate where the at least two stacked dies and the first set of conductive elements are surrounded by the first molding compound. Forming a bottom die package encompassing at least one die on a bottom substrate. Providing a thermal contact pad and a seal ring between a top surface of the bottom die package and a bottom surface of the top packaging substrate, and electrically coupling the top die package to the bottom die package with a second set of conductive elements.

Although the embodiments and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations could be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, and composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. In addition, each claim constitutes a separate embodiment, and the combination of various claims and embodiments are within the scope of the disclosure. 

What is claimed is:
 1. A semiconductor device, comprising: a top die package having a plurality of first dies on a top packaging substrate; a bottom die package having at least one second die on a bottom packaging substrate; a first set of conductive elements electrically connecting the top die package and the bottom die package; a thermal contact pad between a top surface of the bottom die package and a bottom surface of the top packaging substrate, wherein the thermal contact pad thermally isolates the bottom die package from the top packaging substrate; and a molding compound surrounding the thermal contact pad, the top packaging substrate, and the bottom die package.
 2. The semiconductor device of claim 1, the top die package comprises a die stack, wherein each die of the plurality of first dies is electrically coupled to the top packaging substrate by one or more wire bonds.
 3. The semiconductor device of claim 1, wherein each first die of the plurality of first dies is in direct physical contact with the top packaging substrate and each first die is electrically coupled to the top packaging substrate by one or more wire bonds.
 4. The semiconductor device of claim 1, wherein a first molding compound covers the top die package, and wherein a second molding compound surrounds the first molding compound and the bottom packaging substrate.
 5. The semiconductor device of claim 1, wherein the thermal contact pad is a non-continuous or ring-shaped thermal contact pad, and further comprising: a seal ring surrounding the non-continuous or ring-shaped thermal contact pad.
 6. The semiconductor device of claim 5, wherein a first molding compound covers the top die package, and wherein a second molding compound surrounds the first molding compound and the bottom packaging substrate; and wherein the second molding compound resides between an outer edge of the non-continuous or ring-shaped thermal contact pad and an inner edge of the seal ring.
 7. The semiconductor device of claim 1, further comprising: a second set of conductive elements electrically coupling the plurality of first dies to the top packaging substrate; and a third set of conductive elements electrically coupling the at least one second die to the bottom packaging substrate.
 8. A semiconductor device comprising: a top die package having at least two stacked dies on a top packaging substrate; a first set of conductive elements electrically coupling the at least two stacked dies to the top packaging substrate; a first molding compound on the top packaging substrate, wherein the first molding compound surrounds the at least two stacked dies and the first set of conductive elements; a bottom die package having at least one die on a bottom substrate; a thermal contact pad and a seal ring between a top surface of the at least one die and a bottom surface of the top packaging substrate; and a second set of conductive elements electrically coupling the top die package to the bottom die package.
 9. The semiconductor device of claim 8, wherein the first set of conductive elements comprises one or more wire bonds which electrically couple each die of the at least two stacked dies to the top packaging substrate.
 10. The semiconductor device of claim 8, further comprising: a third set of conductive elements electrically couples the at least one die to the bottom substrate.
 11. The semiconductor device of claim 10, wherein the third set of conductive elements comprises conductive pads, conductive pillars or conductive vias to electrically couple the at least one die to the bottom substrate.
 12. The semiconductor device of claim 8, further comprising a second molding compound surrounding the first molding compound and the bottom substrate.
 13. The semiconductor device of claim 12, wherein the thermal contact pad comprises a non-continuous or ring-shaped thermal contact pad surrounded by the seal ring.
 14. The semiconductor device of claim 12, wherein the thermal contact pad comprises a solid, continuous material which extends along the top surface of the at least one die on the bottom substrate and which fills the area within the seal ring.
 15. A semiconductor device comprising: a substrate; a first die coupled to a top surface of the substrate; a second die coupled to a bottom surface of the substrate; a thermal contact pad coupling the second die to the bottom surface of the substrate, wherein the thermal contact pad electrically isolates the first die from the second die; and a molding compound over the substrate and surrounding the first and second dies and the thermal contact pad.
 16. The semiconductor device of claim 15, further comprising: a set of conductive elements electrically connecting the first die to the second die, wherein the molding compound is between a portion of the thermal contact pad and at least one conductive element of the set of conductive elements.
 17. The semiconductor device of claim 15, further comprising: a set of conductive elements electrically connecting the first die to the substrate, wherein the molding compound is between a portion of the thermal contact pad and at least one conductive element of the set of conductive elements.
 18. The semiconductor device of claim 15, further comprising: a set of conductive elements electrically connecting the second die to the substrate, wherein the molding compound is between a portion of the thermal contact pad and at least one conductive element of the set of conductive elements.
 19. The semiconductor device of claim 16, further comprising: a first set of conductive elements electrically coupling the first die to the substrate; a second set of conductive elements electrically coupling the second die to the substrate and to the first die; and wherein the molding compound is between a portion of the thermal contact pad and at least one conductive element of the first set of conductive elements or is between a portion of the thermal contact pad and at least one conductive element of the second set of conductive elements.
 20. The semiconductor device of claim 15, further comprising: a seal ring surrounding the thermal contact pad and arranged between the second die and the bottom surface of the substrate. 